Abstract : As an example of a two-phase system, ammonia and the complex compound of ammonia with n-propanol demonstrates the possibility of isotopic separation of nitrogen using the method of chemical exchange using complex formation. An automatic apparatus is described for the isotopic separation by the method of chemical exchange, using the method of thermal reversibility between phases. For the system NH3 - NH3.C3H7OH in a 1.5 meter column at 6C., and with a rate of addition of the complex of 1.0 ml/min over 8 hours, a coefficient of separation of 1.489 was obtained, whereby 15N was concentrated in the liquid phase. (Author)